The present invention relates generally to copy protection. More specifically, the present invention relates to a method and apparatus for providing copy protection to recorded and broadcast data. The present invention applies to video, audio and other types of data recorded on a medium or broadcast to an audience.
With the proliferation of digital recording, the ability to create unauthorized copies of digitally recorded content has become a serious problem for those that have a vested interested in the content. Copyright laws prohibit the unauthorized copying of copyrighted materials. However, copyright laws seldom prevent individuals from unauthorized copying.
Current copy protection schemes typically only provide copy protection to digital content stored on a recording medium, such as a Digital Video Disc (DVD) disc (sometimes also referred to as digital versatile disc). FIG. 1 illustrates a conventional copy protection scheme 10. The copy protection scheme includes a host computer 20, a DVD drive 14 which reads data from a DVD disc 12.
In the copy protection scheme illustrated in FIG. 1, DVD drive 14 is capable of reading DVD disc 12 and passing the data to host computer 20. If the DVD disc 12 is copy protected according to a CSS (Content Scrambling System) scheme, the drive will insist on undergoing an authentication protocol with the host 20 before transferring the scrambled data. The scrambled data may only be unscrambled if the “disc key” and the “title key” are known.
Knowledge of a “global key” is necessary to perform the authentication and the exchange of the “disc” and “title” keys. The “global key” is incorporated in drives and in CSS compatible host systems in protected modules such that a user cannot easily obtain access to the “global key”. The “global key” allows the host to participate in the “authentication” step, which precedes the transfer of the descrambling keys and the scrambled data. Generally, the “global key” is kept confidential among manufacturers to avoid proliferation of the “global key.”
After the authentication protocol has been completed, drive 14 will read disc 12 and obtain “title keys” from a region of the disc which is not accessible to the host, and pass these keys in encrypted form to host 20. The components of the host system 20, which are CSS compliant, are able to decrypt these keys and use the information to descramble the audio/video data subsequently retrieved from the disc.
In this way the CSS scheme prevents easy copying of the data on the disc because “global keys” are necessary to decrypt the descrambling keys, which are necessary to make any sense out of the data, and because the data is passed through user accessible busses only in scrambled form. If a copy of the scrambled data is made, the descrambling keys will be missing.
Copying the descrambled data is made difficult by various techniques, primarily keeping the data off user accessible busses. CSS compliant systems are obligated to inhibit copying of the CSS protected DVD video data. However, CSS encoding does not address the issues of broadcast data and the requirement that the end user be allowed to make a copy for time shifting purposes.
CSS encoding of digital data prevents the unauthorized copying of data stored on a physical medium. However, CSS encoding does not function for content that is broadcast over terrestrial radio frequencies or cable. FIG. 2 illustrates a typical television broadcast communication system. A transmitter 30 transmits audio, video, and/or information data over radio frequencies to an antenna 33. A typical home viewer may possess a set top box 40, a monitor 42, and recording devices 50 and 60.
Antenna 33 receives the data transmitted by transmitter 30 and provides it to set top box 40. Set top box 40 typically demodulates and/or decodes the data transmitted by transmitter 30 and provides a suitable data stream for viewing and/or recording to recorder 50 and monitor 42. A viewer may watch the decoded television signals on monitor 42, or the viewer may wish to record the transmission on recorder 50.
Currently, copyright laws permit a viewer to make a single copy of a transmission for time shifting purposes. That is, a viewer may not be home to view a particular transmission, therefore the viewer may wish to record the transmission and view it at a later time. A consistent problem that has faced broadcasters and content providers is that there is typically nothing to stop a viewer from making multiple generation copies of a transmission. Whether the transmission is broadcast over the airways or through a cable a viewer typically has the ability to make more than one copy of the transmitted content.
Referring back to FIG. 2, the viewer may record the transmitted data on disc 52 using recorder 50. At the same time the viewer may also record the data on disc 63 using recorder 60. Using either one of disc 52 or disc 63 viewer may make an infinite number of copies of the transmitted data.
Currently, copy protection schemes have been utilized to prevent copying of data stored on a medium. However, copy protection schemes typically do not provide copy protection for data that is transmitted. Therefore, there is a need to provide a copy protection scheme that allows a viewer to make one copy of a transmission, but which also prevents further copying after the initial copy is made. Further, the copy protection scheme should also prevent copying of data stored on a recording medium.